1978 kz200 gas leaking into oil

Here is what happened:
1) Starts on 1st or second kick, sounds great.
2) Revs up easily with great power and sound
3) Starts smoking out tailpipe, proportional to rpms.
4) Idle went way up, to like 8,000rpms. Held there, but kept smoking. Now smoking off engine body (not head).
5) I killed it.
6) Opened oil hole (where you fill the oil), smoke in transmission. Can blow in, smoke blows out. Can see about a 1/16" of gas sitting on top of the oil through the viewing port.
7) Pulled the spark plug and kicked it (kickstarter), cylinder NOT full of gas as has been the problem before.

Any idea what might cause this? New head gaskets, Cylinder rings are in correct alignment, maybe a secret O ring type thing somewhere?

It ran for about 5 min real strong before another problem (carb overfilling and FILLING cylinder with gas) killed it. However, during that ordeal no gas got into oil. Then i fixed the carb and ran it again in maybe 3 hours, and above problem started. So why was it holding gas, then not? Could the cylinder rings be jiggling out of alignment so that the gaps line up and leak that way?

Check to ensure the carb float valve is operating properly and not sticking open. Also, check the fuel level in the carb using the clear tube method (see image below) to see if it is set too high or too high due to a sticking float valve. Check your manual for the correct fuel level. Ed

Oh, never thought of the tube method, that is awesome! I will try. Thanks!
p.s. are these captca's in particular really hard for you too?

Nope, fuel level great. Starts smoking out tailpipe about 3 seconds after it starts. pulled spark plug, cylinder full of smoke.

I use a desktop for access and haven't had any problems. I can't say for sure, but you may be experiencing a temporary situation intended to block spammers. If that is the case it should clear up after so many days or so many postings. Ed

That would make sense. Anyone have ideas as to the problem here (the bike, not the captchas)?

A bad petcock and float needles and seats will cause fuel to flow constantly which will cause fuel to overflow into the cylinders and air box

Float is cutting off fuel before any overflowing is happening. Keeps the fuel level around 5mm below the gasket on the carb (where the bottom comes off). I ordered new cylinder rings for $25 bucks and am going to try that. If that fails, I am out of answers. Hopefully I will get to ride soon!!! I have only ridden a couple times in my life, this was a bike my dad gave me to learn to ride on. Instead, I have learned mechanic skills! $600 and 2 years later, I am still hoping to ride it eventually. It sure was fun to ride a few blocks before it died and I had to push it back! Cheers.

Now that the carb overflow condition has been corrected, what is the current issue?

Are valve clearances within specs?
Insufficient valve clearance may permit seating enough to allow a cold engine to start and run until the engine warms. Then the warm engine loses compression as the insufficient valve clearance disallows proper seating.

What are results of cold compression test?
Is compression within specs?
Does adding a teaspoon of motor oil through the spark plug hole produce different compression test results?

A leak down test could be performed to assess general condition of the engine.

A leak down test injects air pressure through the spark plug hole to pressurize the combustion chamber.

Can perform a poor man's leak down test by introducing compressed air into a spark plug hole and listening to where it escapes from the combustion clamber. This may be done at TDC or any other cam positions where both valves are fully closed. Top dead center (TDC) is when the piston is at its highest position. An easy way to tell TDC is by alignment of the T mark with the case mark when viewed through the timing window.

May introduce a spurt of compressed air by using a rubber cone-tip blow gun (rubber air nozzle) held into the spark plug hole. And of course keep holding it in position to keep air from coming back out the spark plug hole while listening for escaping air at other places. The air compressor should not be running while listening because the noise will likely drown out any sound of escaping air. Or just use a portable compressed air tank.

Air heard escaping from exhaust port indicates exhaust valve not fully closing (perhaps too tight clearance or damaged valve or valve seat).

Air heard escaping from carb intake indicates intake valve not fully closing (perhaps too tight clearance or damaged valve or valve seat).

Air heard escaping from crankcase breather indicates loss of compression past rings into crankcase (perhaps worn piston rings or cylinders).

Air heard escaping from head gasket area indicates indicates loss of compression past head gasket (perhaps due to a blown head gasket).

A leaking valve may sometimes be resolved by adjusting the clearance to within specs.

A leaking head gasket may sometimes be resolved by torquing the head fasteners when the engine is stone cold (such as after sitting overnight).

Good Fortune!

Is the ignition timing advancer functioning correctly?
Or is it perhaps sticking?
The weight arm pivots may require lubing, or there may be some other reason for malfunction.

Am uncertain about the bike at hand, but on some models, the advancer weight arm pivots may be lubed by access through the timing inspection window.

Good Fortune!

If needed, may download a service manual with this link:

Click here > www.facebook.com/media/set/?set=a.164610...5236331&l=b7a818679d

Good Fortune!

Thank you all for your help! I replaced the piston rings, reseated the valves (one of the seats was in two pieces :ohmy: ) and lapped the valves. it helped! In my genius I idled the bike at 7,000rpms for like 5 min, to burn off oil/dust/nasties that has accumulated over the past 3 years of not running. It ran strong, exhaust pipe smoked a bunch then stopped, then the block smoked a lot and slowed down, then the bike died and would not re-start. Think I get it too hot:(